When temperatures dropped below freezing and stayed there for 48 hours, the team turned on the wires in half of the plots. Two days later, they allowed the soil in these plots to freeze again. Over the course of the winter, the technique added five extra freeze-thaw cycles to the three that occurred naturally. After harvesting, drying, and weighing the plants the following summer, measurements showed that heated plots contained 10 percent more biomass above ground than unheated plots did. In a paper in the journal New Phytologist, the researchers speculated that thawing and refreezing increases microbial activity and breaks up the soil, making plants more productive. "Winter...is a time during which the plants were proposed to do nothing," Kreyling said. "It is astonishing that they seem to be able to take up nutrients that become available during the freeze-thaw events." Not all news was good news, though. Results showed that roots were shorter in the heated plots. The same weather conditions might be harder on other plant species, added Hugh Henry, a plant ecologist at the University of Western Ontario. And, he said, nutrients that leach out of the soil during freezing and thawing cycles most likely end up in rivers, streams, and lakes, where they cause algal blooms and other problems. "This indicates," Henry said, "that changes in climate and more extreme climate events could potentially have fairly large effects on nutrient availability and the way plants grow." Related Links: |
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